1. Field of the Invention
This invention relates to a generator-motor for internal combustion engines, which operates not only as a generator for converting energy of rotation of an internal combustion engine into electric energy, but also as a motor for generating such a torque as to assist or suppress the torque generated by the internal combustion engine.
2. Description of the Related Art
A typical generator for internal combustion engines mounted on vehicles or ships includes an alternator (ACG ) with its rotating shaft mechanically coupled to a crank shaft of an internal combustion engine (generally, through an alternator belt); a rectifier for converting AC power into DC power, the AC power generated by the alternator according to the rotating speed of the internal combustion engine; and a regulator for controlling the voltage level of the DC power according to the voltage across a battery. FIG. 2 is a schematic diagram showing a structure of a conventional alternator 50, in which a DC field coil 53 is wound around a rotor 52 integrally formed with the rotating shaft and a three-phase coil 55 is wound around a stator 54. Whenever the DC field coil 53 is excited by supplying direct current from the battery (not shown), the rotor 52 is rotated to create an alternating magnetic field. Consequently, the three-phase coil 55 of the stator 54 generates AC power with a frequency corresponding to the rotation speed of the rotor 52. In some cases, the rotor 52 may be provided with a permanent magnet instead of the DC field coil 53.
With such an internal combustion engine for vehicles or the like, since the rotor 52 of the alternator 50 is mechanically coupled to the crankshaft of the internal combustion engine even when the battery is fully charged and power generation is no longer necessary, the rotor 52 is rotated constantly to cause rotation loss due to belt driving torque or cooling fan resistance.